Problem with those voltage indicators is with all these Chinese PWM mods out now, they don't work. You actually need a higher-end multi-meter than can measure a PWM output. Though they work great for a regular ol' battey mod. Good trouble-shooting tool for that.
BTW, there are two connections in the picture of the atomizer checker, it's just there's a black cartomizer in one so it's not obvious it's there. That had me confused for a bit the first time I saw that photo at MadVapes.